Take a look at what script is set to run when you open the file. If you don't know which script, select File | File Options... and you'll see it listed. Somewhere in that script is a reference to a table that is no longer part of your file.
If you have a copy of fmp advanced, launch filemaker without opening this file, enable the debugger and then open the file. You'll then be able to step through the script one line at a time to see which step is the culprit.
Once you have that sorted out, you can ad a Show Custom Dialog step to your script to display a custom pop-up how and when you want it to.